java - 使用JAVA对象和输入数据进行赋值

Question

所以我的任务是创建一个名为 city 的对象，并具有城市的经度、纬度和名称，然后询问城市的数量，然后用户将名称、经度和纬度输入到数组中进行访问。我将如何利用我现在所拥有的来实现这一目标？

import java.util.Scanner;

public class Assignment3 {

    public static void main(String[] args) {

        Scanner lat = new Scanner(System.in);  //for double data
        Scanner lon = new Scanner(System.in);  //for double data
        Scanner city = new Scanner(System.in); //for string data
        Scanner in = new Scanner(System.in);  //for int

        System.out.print("How many cities? ");
        int number = in.nextInt();


        City [] cities = new City [number];

        for(int i = 1; i <= number; i++){

            System.out.println("City # " + i);
            System.out.print("Enter name: " );
            String name = city.Next();
            System.out.print("Enter longitude: ");
            double longitude = lon.nextDouble();
            System.out.println("Enter latitude: ");
            double latitude = lat.nextDouble();

        }

    }

}


public class City {

    String name;      //name of cities
    double lon, lat;  //longitude & latitude

    City(String name, double lon, double lat) 
    {
        this.name = name;
        this.lon = lon;
        this.lat = lat;
    }




    public void report(){    //should report current position of a city

        System.out.println("City: " + this.name); // displays city name
        System.out.println("Longitude: " + this.lon);  //displays longitude
        System.out.println("Latitude: " + this.lat);    //displays latitude
    }

    public double distanceFrom(City otherCity){  //should calculate the distance
        return 0;
    }
}

重点是，您可以询问城市的直接位置以及它们之间的距离。非常感谢任何帮助，谢谢

Answer 1

您可以通过这种简单的方法实现这一点:

为您希望用户输入的每个属性定义 City 类的 setter 实例方法，然后在主程序中迭代城市的每个对象并设置其信息:

public static void main(String[] args) {

        Scanner input = new Scanner(System.in); 
        System.out.print("How many cities? ");
        int number = input.nextInt();
        City [] cities = new City [number];
         for(int i = 0; i < number; i++){
            cities[i] = new City(); // create new object of City
            System.out.println("City # " + (i+1));
            System.out.print("Enter name: " );
            String name = input.next();
            cities[i].setName(name);
            System.out.print("Enter longitude: ");
            double longitude = input.nextDouble();
            cities[i].setLongitude(longitude);
            System.out.print("Enter latitude: ");
            double latitude = input.nextDouble();
            cities[i].setLatitude(latitude);
        }
}

public class City {

    private String name;      //name of cities
    private double lon, lat;  //longitude & latitude

    City(){  // default constructor
       name="";
       this.lon = 0;
       this.lat = 0;
    }

    City(String name, double lon, double lat) 
    {
        this.name = name;
        this.lon = lon;
        this.lat = lat;
    } 

    public void setName(String n){
         name = n;
    }
    public void setLongitude(double longitude){
         lon = longitude;
    }
    public void setLatitude(double latitude){
         lat = latitude;
    }
}